1. Field of the Invention
The present invention relates to an oily external composition for skin, and in particular, the oily external composition for skin containing zinc oxide complex powder.
2. Prior Art
Conventionally, for protecting skin from ultraviolet rays, some powders such as zinc oxide and titanium dioxide are added in oily external composition for skin. It is difficult to disperse these inorganic powders in oil base, because the surface of said powders generally has hydrophilic property. Concerning emulsion cosmetics (a surfactant is added to oil phase containing powder, and water phase is added to therein and emulsified), sometimes aggregation occurs due to interaction among powder, surfactant and water. As a result, the composition lacks its stability and the functions of powder itself are not shown fully.
For the purpose of improving dispersibility of powder, many kinds of cosmetic compositions are developed; such as cosmetics comprising lipophilic powder whose surface is hydrophobicized [for example complex powder that zinc oxide is covered with magnesium aluminate metasilicate (Japanese Patent Publication Hei 1-308819), cosmetics comprising complex powder that zinc oxide is covered with fluorine modified silicone (Japanese Patent Publication Hei 7-277914)] and cosmetics that powder is disperses in oil dispersion medium with particular dispersant (Japanese Patent Publication Hei 9-208438).
In the above cosmetics, although dispersibility of powder in oil is improved to some extent, it is not enough. And it is difficult to exhibit function that zinc oxide itself originally owns, because its surface is covered fully.